Refer to the following letter and symbol series and answer the question that follows.
Counting to be done from left to right only.
(Left) D K & Ω # E S Y C + * A B @ R T % U $ £ Q G (Right)

How many such letters are there each of which is immediately preceded by another letter and also immediately followed by a symbol?

The correct option is 4.

Let's analyze the given series step-by-step to find the letters that satisfy the given conditions.
The series is read from left to right:
D K & Ω # E S Y C + * A B @ R T % U $ £ Q G

We need to find letters that satisfy two conditions simultaneously:
1. Immediately preceded by another letter (i.e., Letter-Letter)
2. Immediately followed by a symbol (i.e., Letter-Symbol)

Combining these two conditions, we are looking for the pattern: Letter - Letter - Symbol.

Let's scan the series from left to right to identify all such patterns:

1. The first letter is D. It has no letter preceding it.
2. K is preceded by letter D, but followed by the symbol &. Thus, the sequence D K & matches the pattern (Letter - Letter - Symbol). This is our first match.
3. E is preceded by the symbol #.
4. S is preceded by letter E, but followed by letter Y.
5. Y is preceded by letter S, but followed by letter C.
6. C is preceded by letter Y, and followed by the symbol +. Thus, the sequence Y C + matches the pattern (Letter - Letter - Symbol). This is our second match.
7. A is preceded by the symbol *.
8. B is preceded by letter A, and followed by the symbol @. Thus, the sequence A B @ matches the pattern (Letter - Letter - Symbol). This is our third match.
9. R is preceded by the symbol @.
10. T is preceded by letter R, and followed by the symbol %. Thus, the sequence R T % matches the pattern (Letter - Letter - Symbol). This is our fourth match.
11. U is preceded by the symbol %.
12. Q is preceded by the symbol £.
13. G is preceded by letter Q, but is not followed by any symbol.

The 4 matching groups are:
1. D K & (Letter K is preceded by letter D and followed by symbol &)
2. Y C + (Letter C is preceded by letter Y and followed by symbol +)
3. A B @ (Letter B is preceded by letter A and followed by symbol @)
4. R T % (Letter T is preceded by letter R and followed by symbol %)

Therefore, there are exactly 4 such letters.